1. Field of the Invention
The present invention relates to a process for producing a vinyl chloride polymer for matted moldings by suspension polymerization. More particularly, it is concerned with a process for producing a vinyl chloride polymer as a molding material suitable for high-quality matted products, said process being possible owing to the improvement in the method of charging a polyfunctional monomer.
2. Description of the Prior Art
It is known that the production of a vinyl chloride polymer for matted moldings by suspension polymerization in an aqueous medium is accomplished by the addition of a cross-linking agent which is a polyfunctional monomer having 2 or more ethylenic double bonds in the molecule. The charging of such a polyfunctional monomer into the suspension system may be made batchwise before polymerization or intermittently or continuously during polymerization. In either cases, the polyfunctional monomer is added as such or after dilution with a solvent such as toluene, benzene and the like, for the control of insoluble gel content.
The conventional process mentioned above, however, gives rise to a vinyl chloride polymer for matted moldings which contains a large number of fish-eyes.
With the recent expansion of their applications, there has arisen a strict requirement for the quality of vinyl chloride polymers for matted moldings. It is desirable that the vinyl chloride polymer for film and sheet should contain as few fish-eyes as possible.